Unregulated Contaminant Monitoring Rule 2025 Results

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(UCMR 5) – 2025 Results 

As part of the U.S. Environmental Protection Agency’s (EPA) Fifth Unregulated Contaminant Monitoring Rule (UCMR 5), the City of Thornton Water System tested our drinking water for per- and polyfluoroalkyl substances (PFAS) in July 2025.

What we found:
All PFAS tested were not detected in our finished drinking water. Laboratory results showed concentrations below the minimum reporting levels set by EPA.

Contaminant     Date Sampled     Result               EPA Reporting Level                        PFTA                 7/23/202             Not Detected    (<0.008 µg/L)0.008µg/ LPFTrDA           7/23/2025           Not Detected    (<0.007 µg/L)0.007µg/ LNEtFOSAA     7/23/2025           Not Detected    (<0.005 µg/L)0.005µg/ LNMeFOSAA   7/23/2025            Not Detected    (<0.006 µg/L)0.006 µg/L 

What this means:

• These substances were not detected in your drinking water at levels above EPA’s reporting limits.
   
• EPA has issued health advisory levels for some PFAS compounds, but none were found in Thornton’s water at or above those levels.
   
• UCMR testing helps the EPA and states determine the extent of these contaminants and whether future regulations are necessary.
   

No action is required by the City or residents at this time.

For more information about PFAS and UCMR 5 monitoring, visit EPA’s website: https://www.epa.gov/dwucmr.